Composition and process of preparing same



Patented Oct. 17, 19 44 U ITED STATE 2.300.045 oomosrrlorz am) nocass Imamamcaamn PATENT, QF E Donald s. Bruce and m1. 1 mums, sow-f ville, N.J.,

poration, New York.

- New York No Drawinz- Application December Serial Nascent j.-

. Claims. (01-. zoo-cs) This invention relates to a product' and processof preparing a composition containing asbestos. fibres.resinouscomponents and sulphur. It relates particularly to the method ofpreparation of a composition and to a composition suitable for heattreatment in which the color of the final assignors to Johns-ManvllleGor- N. Y..; a corporation or product'is substantially uniform andconsistent at all times.

It has heretofore been known that in compositions containing asbestosfibres and resinous I components, particularly Bakelite resin, the'colorof the final composition has atendency to acquire a pinkish cast. Thisdiscoloration in some cases tion 01' components were. prepared:

is quite uniform'throughout the product and in other cases-isspotty, butas a general rule it is' undesirable infcommerce.

. that it is substantially impossible to eliminate It has been found theundesirable discoloration, eventhough the composition had admixedthereto materials such as carbon black.

- It is an object of the present'invention pre- Ipare a compositionsuitable for heat treatment and adapted tobe molded into materials suchas brake bands, clutches or other products wherein synthetic resins andasbestos fibres are used in combination without discoloration.

It is also an objectof the present invention to prepare an asbestosfibre and resinous composition which will not have a tendency to developa pink discolorationduring storage of the uncured matrial practice.

Additional objects of the invention will become I Bakellteresin Powderedapparent to those skilled in the art .upon the application of thepresentimprovement in indus- Broadly stated, the invention comprises the adto-acomposition containing asbestos fibres and dition of sulphur inrelatively small quantities resinous components. The'composition alsopreferably contains pulverized or powdered carbon 'for purposesordinarily attributed to the use of such carbonaceous materials incompositions suitable for brake linings or similar materials; Thesulphur may be in.any form, such-as flowers of sulphur or the like. Ithas been found that ii the amount of sulphur added to the composition isnot appreciably below 1.25%,"based on the dry weight of the composition,"the pink discoloration ordinarily ob-' tained in the absence of sulphurdoes not occur. If the quantity'ofsulphur added is appreciably below1.25%, based on the dry weight of theoomposition, the depth of the pinkdiscoloration varies from a condition considered satisfactory to onedefinitely unsatisfactory. Under thesecircum- .rormulation B.

is, .1941} stances,

occurred, having faint traces of pink discolorationnwhile in other casesno discoloration oc- The invention may. .be more fully understoodby'reference to the following illustrated examples. A Eamnple I'Compositions containing-the following distriburammetion A Formulation Bbon black Sulphur I 5% was The compositions were prepared by dry mixingthe several components together in order to obtainuniiorm distributionor all or the materials and th adding water a'sspecifled thereto. The

composition as prepared under formulation A- tends to develop a pinkcolor either during'drying of the uncured materials or during the bakingoperation I when the "composition ,is placed in molds. The compositionsas prepared under for mulation B did not develop a pink discolorationeither during storage or the'uncured material's, during subsequentbaking operations, or during storage. oi'the fully baked compositions.This inhibiting effect of discoloration is due primarily to the presenceof the sulphur as illustrated tram le-Ir i The following composition wasplaced in an agitator and mixed for ten-minutes.

The required amount or water. asindicated-informulation, was sprayedinto the agitator is, where the quantity oi sulphur was below 1.25%, insome batches discoloration while the composition was being mixed. Themixed composition was sheeted by known methods and cut into individualsheets. The individual sheets were then subjected to a hydraulicpressure of approximately 1600 lbs. per square inch for one minute andthereafter dried in an oven on steel plates at 100 F. No pinkdiscoloration occurred in the dried pressed sheets after a period offive days storage under atmospheric conditions.

The above sheets were then cut into sections and pressed in a brakeblock mold using a unit pressure of approximately 2000 lbs. per squareinch and cured ,for about 30 minutes under 90 lbs. steam pressure. Awaste scrap material such as results from cutting the sheets during themanufacture of brake and clutch bands, may be ground up for reuse asservice sheet scrap in the compositions of Examples III and III. Afterthe compressing action, the sections were placed in an oven' and bakedfor 12 hours at about 100 F. During the entire operation and also in thefinished product, there was no-suggestion of a pink discoloration of thematerials.

Example III Another composition containing the following components:

Asbestos fibres 15 lbs. oz.

Powdered resin 4 lbs. 8 oz. Powdered carbon black v 0 lbs. 14 oz.Service sheet scrap (screened) lbs. 3 oz. Sulphur Olbs. 6oz.

30 lbs. 15 oz. Water 4 lbs. 0 oz.

34 lbs. 15 oz.

The above materials were treated in substantially the same manner asdescribed under Example II, and after the various treatments, there wasno suggestion of any pink discoloration in the final product. i

The use of sulphur to prevent discoloration in compositions isespecially effective in compositions in which phenolic resins andasbestos fibres I are present. The pink discoloration in compositionscontaining asbestos fibres and phenolic resins is more pronounced whenunmodified phenol formaldehyde type resins are used. However, if sulphuris used as described above, no pink discoloration of the productsoccurs. Oil modified phenol formaldehyde resins give less pinkdiscoloration than unmodified resins, but, through the addition ofsulphur, the pink discoloration in products containing oil modifiedresins will be eliminated.

It should be understood that the details of the description set forthare only for purposes of illustration and that the invention is to belimited only by the scope of the appended claims.

What we claim is:

1. A molding mixture consisting essentially of a major proportion ofasbestos fibers and sufilcient phenol-formaldehyde resin to provide aheat curable bond, said mixture being rendered color stable by thepresence therein of free sulphur, in-

amount constituting l.25'5% of the dry weight change which comprises,incorporating in said,

mixture free sulphur in amount sufiicient to inhibit color change of themixture both during storage and during pressure molding and heat curingoperations thereon, said sulphur being added to the amount constituting1.25-5% of the dry weight of the fiber-resin mixture.

DONALD S. BRUCE. RALPH T. HALS'I'EAD.

